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Re: Re: Compile forgets assigned values inside Do unless they are initialised

  • To: mathgroup at smc.vnet.net
  • Subject: [mg82238] Re: [mg82207] Re: Compile forgets assigned values inside Do unless they are initialised
  • From: DrMajorBob <drmajorbob at bigfoot.com>
  • Date: Tue, 16 Oct 2007 03:21:59 -0400 (EDT)
  • References: <fepss7$gi3$1@smc.vnet.net> <33239569.1192447162247.JavaMail.root@m35>
  • Reply-to: drmajorbob at bigfoot.com

> Yes. If one wants to compile an expression that uses local symbols, then
> these local symbols must be initialized at the beginning of the Module
> (or Block) construct. See ref/message/Compile/initvar.

ref/message/Compile/initvar is precious little to go on, and the following  
seems to contradict your thesis:

Compile[{},Block[{x},x=2]]
%[]

CompiledFunction[{},Block[{x},x=2],-CompiledCode-]
2

Precisely how "late" is "too late"?

Bobby

On Mon, 15 Oct 2007 00:18:55 -0500, Jean-Marc Gulliet  
<jeanmarc.gulliet at gmail.com> wrote:

> Andrew Moylan wrote:
>
>> In the following example, although var is assigned a value, these are
>
> The value is set to late in your example (see below).
>
>> "forgotten" and an error occurs when it is returned as the result of the
>
> The value has not been "forgotten" since it has never been assigned to
> the symbol.
>
>> compiled function:
>>
>> Compile[{},
>>   Module[
>>    {var},
>>    Do[
>>     var = 0.;,
>>     {10}
>>     ];
>>    var
>>    ]
>>   ][]
>>
>>>> Compile::initvar: The variable var has not been initialized or has 
>>>> been
>> initialized to Null.
>>
>>
>> But if var is initialised (to any Real value at all), then all  
>> subsequents
>> assignments to it are "remembered":
>>
>> Compile[{},
>>   Module[
>>    {var = 1.},
>>    Do[
>>     var = 0.;,
>>     {10}
>>     ];
>>    var
>>    ]
>>   ][]
>>
>>>> 0.
>>
>> Is this the expected behaviour?
>
> Yes. If one wants to compile an expression that uses local symbols, then
> these local symbols must be initialized at the beginning of the Module
> (or Block) construct. See ref/message/Compile/initvar.
>
> Regards,



-- 

DrMajorBob at bigfoot.com


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